Platform positioning mechanism

ABSTRACT

Through a system of beams and rollers, an upper base is mounted for horizontal movement at or near the ceiling of a room. A vertical mast is fixed at its upper end to the upper base for integral movement therewith. A movable mast is telescoped about the fixed mast and moves vertically thereon. A carriage slides vertically on the movable mast and has an opening for the passage of both masts so that it may be elevated to the upper end of the movable mast when the movable mast is lifted to its uppermost position on the fixed mast. An operator&#39;&#39;s platform rotates about the carriage on a circular bearing having an opening through which the two masts extend.

United States Patent 1 [72] Inventor Standly J. Gustetic Euclid, Ohio[21] AppLNo. 861,066 [221 Filed Sept. 25, 1969 [45] Patented Aug. 31,1971 [73] Assignee Eaton Yale 8: Towne, Inc.

Cleveland, Ohio [54] PLATFORM POSITIONING MECHANISM 13 Claims, 10Drawing Figs.

[52] US. Cl 182/37, 182/142, 182/150 [51] 1nt.Cl E04g3/10 [50] FieldotSear-ch 182/37, 142,150,l28,63,148;212/l28,125

[56] References Cited I UNITED STATES PATENTS 2,553,378 5/1951 Miller182/37 Primary Examiner- Reinaldo P. Machado Attorney-Teagno and ToddyABSTRACT: Through a system of beams and rollers, an upper base ismounted for horizontal movement at or near the ceiling of a room. Avertical mast is fixed at its upper end to the upper base for integralmovement therewith. A movable mast is telescoped about the fixed mastand moves vertically thereon. A carriage slides vertically on themovable mast and has an opening for the passage of 150th masts so thatit may be elevated to the upper end of the movable mast when the movablemast is lifted to its uppermost position on the fixed mast. An operatorsplatform rotates about the carriage on a circular bearing having anopening through which the two masts extend.

AEROPLANE PATENTEH was] I97! SHEET 1 [1F 6 FIG.

AEROPLANE alllllllllllllllllllllll I HflH -I I NNNH INVENTOR.

STANLEY J'- GUSTETIC BY:

ATTORNEY.

PATENTEI] M1831 I971 3,602,335

SHEET 2 0r 6 3| INVENTOR.

BY STANLEY I GU87? TIC F e 7 ATTORNEY.

ATENIEH nus31 3 602 335 SHEEI 5 OF 6 [Ill/Ill IN VENT OR.

e, BYSTANLEY .zeusrmc N AT TO RN EY- ATENTEH M1831 11 3 502 335 saw 6 0F6 65 INVENTOR.

sTQ NLEY .Z'GUSTETIC ATTORNEY.

PLATFORM POSITIONING MECHANISM BACKGROUND OF INVENTION This inventionrelates to a combination of the class in which a carriage is mounted forvertical movement on a mast, the mast itself being mounted for lateralmovement in a room or the like so as to bring the carriage into anyposition in the room. More particularly, the invention relates to amachine of the particular class in which the carriage is adapted tocarry an operator into positions to perform particular operations.Through proper manipulation of the mast and carriage, the operator maybe moved to any position laterally and vertically within the room forthe carrying out of any desired type of operation.

PRIOR ART There is much prior art available in this field-Thus, it isquite old in the art to have an upper base mounted for horizontalmovement adjacent a ceiling, through the utilization of a system ofbeams and rollers. On the base, there is usually mounted a downwardlyextending mast that is rotatable relatively to the base. The carriage isusually mounted for vertical movement on the mast, and as the mastrotates the carriage rotates therewith.

As those skilled in the art will readily appreciate, the use of a verylong mast as may be required in a room having a very high ceiling, andthe positioning of a relatively heavy carriage on the mast, will exertgreat stresses on the bearings that mount the mast for rotationrelatively to the base. It is further well to note that the mast, if itis to allow the carriage to move to a low position, will have to be ofthat length approaching the floor. Therefore, the lower end of the mastis always in a position where it prevents the movement of the entireassembly past machinery or other structures that are on the floor of theroom. Any lateral stress exerted at the end of the mast will, throughthe considerable length of the mast, cause great damage at the uppermostbearing.

OUTLINE OF INVENTION My invention is particularly adapted for use in aroom having an extremely high ceiling, such as a room in which anairplane is to be serviced orassembled. As a feature of the invention, Iutilize a mast that is fixed at its upper end to the upper base of myassembly, thereby contributing an extremely rigid construction such ascannot be obtained where the mast is mounted on a bearing for rotationrelatively to the base as earlier outlined. As a further feature of theinvention, in order to facilitate movement of my entire assembly andcarriage without undue hindrance by machinery resting on the floor ofthe room, the mast is preferably made of two telescoping parts. Thus,there is an outer part adapted for movement on an inner part, which isthat part of the mast fixed at its upper end to the base. As a furtherparticular feature of the invention, the outer or movable part is in theform of a tube that is telescoped about the inner or fixed mast, and ispreferably raised and lowered relatively to the fixed mast as byconventional hoist drum and cable.

As a further particular feature of the invention, l utilize a carriagethat is adapted to be raised and lowered relatively to the tubularmovable mast, with the movable mast extending through an opening of boththe carriage and a platform that is a part of the carriage assembly. Theplatform is rotatable relatively to the carriage as well as the mast,and carries the operator and the various controls of my assembly. As aparticular feature of this portion of the invention, the platform iscounterbalanced by novel means.

Both the movable tubular mast and the fixed or rigid mast may extendthrough the central opening in the carriage and the operators platformin order to permit the movement of the carriage between an extreme lowposition and an extreme upper position. This feature is of extremeimportance.

As a still further particular feature of the invention, the carriage isadapted to be lifted relatively to the movable mast through theutilization of racks mounted on the movable mast and contacted bypinions rotated by hydraulic motors carried on the carriage. It will bewell to emphasize that the utilization of hydraulic motors and pinions,makes possible the elimination of relatively heavy electric motors onthe carriage, which it will be emphasized, does not rotate relatively tothe movable mast. On the carriage platform that does rotate relativelyto the mast, I prefer to mount the motors and pumps for generating thehydraulic pressure that is required to operate the pinions that move thecarriage vertically on themovable mast. The motors and pumps contributebalance as will be set forth. Obviously, the movable mast is movable onthe rigid mast independently of the movement of the carriage on themovable mast.

As part of the concept of my invention, 1 mount the motors and pumps onthat side of the rotating operator's platform opposite the side on whichthe operator stands, thereby effecting counterbalancing of the carriageand platform assembly.

As a still further feature of the invention, I utilize a very novel andsimple means for transmitting hydraulic pressure from the rotatingcarriage platform to the nonrotating carriage, utilizing a single hoseconnected in an extremely novel manner between the carriage and itsplatform.

DESCRIPTION OF DRAWINGS FIG. 1 is a vertical view of the assembly of myinvention showing its relation to the fuselage of an airplane to beserviced. FIG. 2 is an end view of the assembly of FIG. 1. FIG. 3 showsthe assembly of FIG. 1 with the platform rotated and the carriage liftedto a relatively high position to service the upper portion of anairplane. FIG. 4 is an enlarged elevation of the nonrotating carriage onwhich the platform is mounted for rotation. FIG. 5 is a view lookingdownwardly on the assembly of FIG. 4 showing the manner in which thenonrotating carriage is mounted for vertical movement on the tubularmovable mast. FIG. 6 is an enlarged view in elevation showing theassembly of the rotating platform to the nonrotating carriage as wellasparts of means for mounting the carriage on the tubular mast. FIG. 7 isa section along the line-7- 7 of FIG. 6. FIGS. 8, 9 and 10 arediagrammatic views showing the hydraulic line connecting the nonrotatingcarriage and the source of hydraulic fluid pressure on the rotatingplatform.

DESCRIPTION OF A PREFERRED MODIFICATION OF INVENTION Referring now moreparticularly to the drawings, and especially FIG. 1 and 2, the ceilingof the room in which the assembly of my invention is operated isdesignated by the reference letter C, while the floor is designated byreference letter F. The upper base of the machine is designated by thereference letter B and is manufactured from various structural steelmembers as is common in. the art, and when completely assembled, isadapted to be mounted on rails 10 through use of rollers 11. The rails10 are in turn secured to roller carriages 12 that through rollers 13are mounted on a beam 14 secured in a suitable manner to the ceiling C.The mounting is such that the base B may move in a longitudinaldirection relatively to the ceiling, and also in a transverse directionrelatively to the ceiling, so that the base B may be positioned anywherein the room relatively to the ceiling C. The manner in which the base Bis mounted for movement is so very well known in the art, that I havenot shown the construction in detail nor will I describe it in detail,it obviously being not a particular feature of my invention.

The fixed or rigid mast of my invention is designated by referencenumeral 15, and it is secured at its upper end at 16 to the base B so asto be integral with the base and to move integrally with the base. Themast 15 may be fabricated in any manner desired, but in the main, itwill be such as to present, for the purpose of my invention arectangular cross section preferably square. The movable mast of myinvention is designated by reference numeral 20 and it is fabricatedfrom structural members to present the cross-sectional shape bestillustrated in FIG. 5. Naturally the cross section will be such that themast 20 will fit about mast and will move freely vertically relativelythereto. The manner in whichthe movable mast is fabricated is notparticularly important, but it is quite necessary, however, that it belight and strong. In order to contribute to its strength, angular strutssuch as illustrated at 21 in FIG. 2 may be utilized. Also, flanges 22may extend at each comer from the mast as particularly shown in FIG. 5.

For lifting and lowering the tubular mast 20 relatively to the rigid orfixed rnast 15, I utilize a hoist assembly designated by referenceletter H, and embodying a hoisting drum 25 and a hoisting cable 26fastened at one end to the movable tubular mast 20 at 27. The drum 25itself is rotated by the usual electric motor 28. It is quite obvious,that operation of the motor 28 will cause the cable 26 to lift and lowerthe outer tubular mast 20 relatively to the fixed mast 15. I have notillustrated the means for guiding mast 20 relatively to mast 15 becauseany suitable system of rollers may be used.

The carriage assembly of my invention, as already outlined, includes anonrotating carriage designated by reference numeral 30, and a rotatingoperators platform designated generally by reference numeral 31, andmounted on carriage 30 for rotation as from the position of FIG. I tothe position of FIG. 3. The nonrotating carriage 30 may be fabricated inany suitable manner, but its important necessary feature is a squarecentral opening for the movable tubular mast 20, as probably best seenin FIG. 5. There, it will be noted that this central opening is formedby an assembly of horizontal beams, suitably welded or bolted to oneanother. Thus, there is a beam 32 on which are mounted rollers 33 thatcooperate with one surface of the rectangular movable tubular mast 20.The carriage has a further beam 34 at right angles to beam 32 on whichare mounted rollers 35 that cooperate with another surface of thetubular movable upright 20. A further beam designated by referencenumeral 36 is shown with rollers 37 that coact with a third surface ofthe tubular mast 20. In FIGS. 4 and 6 further upper rollers 38 are shownon the carriage 30 for cooperating with a fourth side of the movablemast 20. These rollers do not appear in FIG. 5 because a portion of thestructure in FIG. 5 is not shown in order to better illustrate othermechanism.

Further, as shown in FIG. 6, there are additional rollers mounted on thecarriage 30 below the rollers described above, and these additionalrollers include two pairs of rollers 40 that are also well illustratedin FIG. 7, these rollers cooperating with the rollersalready describedfor securely mounting the nonrotating carriage 30 about the tubularupright 20. Still more rollers 41 are also shown in FIG. 6, these lyingdirectly below the rollers 35. It will now be well appreciated that therelationship of the rollers to the mast is such that the nonrotatingcarriage 30 will be well-mounted for vertical movement on the tubularmast 20, and that the tubular mast will move through a central openingin the carriage 20.

For lifting carriage 30 relatively to the mast 20, I apply to each oftwo opposed surfaces of the tubular mast, a rack 50. The racks 50 may bewelded to the surfaces of the mast so as to become integral portionsthereof as clearly shown in FIG. 5, as well as in FIG. 3 and 6.

Mounted on the carriage 30, as best seen in FIG. 4 and 5, is a lowerhydraulic motor 51, and an upper hydraulic motor 52. Motor 51 operates agear reduction unit 53, while upper hydraulic motor 52 operates a gearreduction unit 54. Gear reduction unit 53 rotates a pinion 55 that is inengagement with one of the racks 50, while gear reduction 54 operates apinion 56 that is in engagement with the other of the racks 50. It willbe obvious that rotation of the pinions by the gear reduction units andthe hydraulic motors 51, 52 will bring about the lifting of the carriage30 relatively to the tubular mast 20. As a particular feature of theinvention, the gear reduction units 53, 54 are irreversible, so thatshould there be a failure of the hydraulic system, as a breakage of ahose transmitting fluid to the motors 51,52 the carriage 30 will notdrop since the gears will hold the pinions 55 and 56 against rotation.The system of rollers I described earlier, securely hold the pinions55,56 against the racks.

I shall now describe the mounting of the operator's platform 31 on thecarriage 30 to complete my carriage assembly. At the lower end of thenonrotating carriage 30 there is mounted a circular gear 60, as is wellillustrated in FIG. 4. This gear is in the form of a ring, and as canalso be seen in FIG. 6, it is secured to the nonrotating carriage 30through welding to a collar 61 that is integral with the carriage 30.

The rotating operators platform 31 of the carriage assembly has acircular ring portion 62 that is inserted into the central opening ofthe circular gear 60, as best seen in FIG. 6. The part 62 is formed witha circular bearing groove on its periphery that coacts with the seriesof ball bearings 63 lying in a bearing groove formed on the innersurface of the gear 60. Through the particular arrangement, it isreadily seen that ring 62 will rotate. relatively to the gear 60, andwill also be supported by the gear 60. I shall shortly describe how gear60 is utilized to rotate the operators platform 31.

A series of bolts 64, one of which is shown in FIG. 6, secure to thering 62 for movement therewith, the baseplate 65 of the operator'splatform 31 which extends laterally at both sides of the tubular upright20. As illustrated in FIG. 6, the right-hand portion of plate 65 carriesthe operators stand S on which may stand an operator. Suitable railings66 are formed on the stand to protect the operator, and at 67 and 68,the various controls for the several motors required to manipulate theplatform 31, the carriage 30, and the masts l5 and 20, as well as theupper base B, will be mounted.

In counterbalancing relation to the parts of the platform 31, I utilizean assembly 70, in which may be included motors and pumps for developingthe hydraulic pressure that is required for the operation of the twohydraulic motors 51, 52 described in connection with FIG. 4, these beingmotors that actuate the pinions 55, 56 for lifting and lowering thecarriage relatively to the tubular upright 20. I shall presentlydescribe the manner in which fluid is directed from assembly 70 towardsthe motors 51, 52.

The fluid pressure developed at 70 is also directed to a hydraulic motor71 best illustrated in FIG. 6. This motor, which is carried on platform31, drives a pinion 72 that is in engagement with the gear 60.Obviously, by rotation of the pinion 72, the rotatable platform 31 ofthe carriage assembly including base 65 and ring 62 will rotate on theball bearings 63 relatively to the ring gear 60.

Because the source of fluid pressure at 70 rotates relatively to thehydraulic motors 51, 52 which are on carriage 30, it is necessary todevelop means for transporting the fluid under pressure from the source70 to the motors 51, 52. As earlier outlined, because the electricmotors and the pumps for developing fluid pressure at 70 are locatedopposite the operators stand S, they act to counterbalance the weight atS in a most effective manner. Were the apparatus at 70 positioned on thenonrotating carriage 30, the lack of counterbalancing would require theuse of more massive and heavier parts, as is obvious. It is alsoimportant to consider, that the locating of the hydraulic motor 71 asshown in FIG. 6, places it very close to the supply of fluid pressure70, so that fluid pressure need only be directed through relatively morecomplex means to the two motors 51, 52.

This last is accomplished best as is illustrated in FIG. 8, 9 and 10taken in conjunction with FIG. 6. l have, for simplification, not shownthe feature in other figures. Thus, in FIG. 6 there is shown a hose 75extending from apparatus 70 to a connection at 76 on nonrotatingcarriage 30 from which connection fluid is directed to the two hydraulicmotors 51 and 52 by rigid conventional means not shown. The utilizationof the hose 75 in my combination is extremely novel as will appear fromastudy of diagrammatic FIGS. 8, 9 and 10. In FIG. 8 the rotatingplatform 31 is in its position relatively to the nonrotating carriage30, that is illustrated also in FIG. 6. The connection of one end of thehose 75 to the source of fluid pressure at 70 is designated by referencenumeral 77. As already indicated, the hose 75 is secured at its otherend to a connection 76 fixed relatively to the nonrotating carriage 30.Let us assume now that the rotating platform portion 31 is rotatedrelatively to the ring gear 60 by motor 71 and pinion 72 (FIG. 6) fromthe position of FIG. 8 to the position of FIG. 9. In FIG. 9 it will benoted that the hose 75 has the shape substantially that of a U, and hasnot in anyway interfered with rotation of the platform 31. The extremerotation of the platform 31 from FIG. 8 is illustrated in FIG. 10, wherethere has been about 90 further rotation from the position of FIG. 9. Inthis final position, it will be noted again that hose 75 has in no wayinterfered with the movement of the rotating platform 31 of the carriageassembly. It is rather obvious that by the very simple means that I haveshown and described, it is possible to actuate the motors 51, 52 foroperating the pinions 55, 56 to raise and lower the carriage 30, whileutilizing a source of fluid pressure that rotates relatively to themotors and may contribute a counterbalancing function. v

It will be well now to summarize the manner in which the parts of myinvention operate to contribute the various features earlier outlined.As can be seen in FIG. 1, the carriage and platform 31 can be lowered toan extremely low position where a workman on stand S is actually underpart of the fuselage of the airplane shown in that figure. The carriagemay also be located as shown in FIG. 3, where the operator on stand S isable to contact the upper portion of the fuselage of the airplane. Itwill be appreciated that to reach the position of FIG. 3 from theposition of FIG. 1, the carriage 30 has been moved upward by operationof the pinions 55, 56 in coaction with the racks 50. At the same time,by manipulation of the controls at 68, the operator has brought aboutthe operation of the hoist H for raising the tubular mast 20 relativelyto the fixed rigid mast 15. It will be appreciated that during movementof the movable mast 20 relatively to the mast by hoist H, the carriageis elevated independently through operation of the pinions 55,56 as justdescribed. This independent action of the hoist and pinions willcontribute extremely swift lifting movement to the carriage, since theelectric motor 28' of the hoist II will be operating the same time thatthe two hydraulic motors 51, 52 are operating to bring about the liftingmovement of the carriage on mast 20. Further, operation of suitablecontrols at the console 68 will also bring about the rotation of theplatform 31 relatively to carriage 30 through pinion 72 and gear 60 asthe said carriage is being elevated. An operator on stand S may now workon the upper part of the airplane as seen in FIG. 3.

It will be noted that in FIG. 3 the movable mast and fixed mast 15 areboth in the central opening of carriage 30 and platform 31. This hasmade possible the upward movement of the carriage and platform. It willalso be noted that the lower end of mast 20 is far above the floor F soas to make possible its free movement with the upper base B and fixedmast 15.

Thus, the novel use of telescoping rigid and movable masts,

together with the novel carriage 30 and its opening for the masts,contributes extremely valuable features.

I do believe that the very considerable merits of my invention will nowbe apparent to those skilled in the art.

I now claim:

1. In a combination of the class described, an upper base mounted forhorizontal movement relatively to an upper structure, a verticallypositioned mast fixed at its upper end to said base so as to become anintegral rigid part thereof, a movable mast mounted for verticalmovement on said rigid mast, means for imparting vertical movement tosaid movable mast relatively to said rigid mast, a carriage mounted forvertical movement on said movable mast, means whereby said carriage ismoved vertically relatively to said movable mast and together with saidmovable mast relatively to said rigid mast, said carriage having avertical opening for the passage of both said masts whereby saidcarriage may be lifted vertically relatively to both said masts whilecompletely encompassing both said masts, said carriage having ahorizontal circular bearing formed outwardly about said verticalopening, and a platform rotatably mounted on said circular bearing andalso formed with an opening for said masts. I

2. In the combination of claim I the feature that said meanswhereby'said carriage is moved vertically comprises a rack secured to avertical surface of said movable mast and a motor driven pinion on saidcarriage.

3. In the combination of claim 2, the feature that the motor drivingsaid pinion is a hydraulic motor, a source of hydraulic pressure forsaid motor on said platform, and means for connecting said source ofhydraulic pressure to said motor.

4. In the combination of claim 4, the feature that said means forconnecting said source of hydraulic pressure to said motor is a hoseconnected at one end thereof to said hydraulic pressure source and atthe other end to a conduit fixed on said carriage, said fixed conduitand hydraulic pressure source being so positioned relatively to saidhose that said hose forms a substantial U between said fixed conduit andsaid hydraulic pressure source when said platform is rotated to a pointsubstantially midway of two extreme points relatively to said carriage.

5. In the combination of claim I, the feature that the means forimparting vertical movement to said movable mast are power operated,independent power means comprising the means for lifting and loweringsaid carriage, power means for rotating said platform relatively to saidcarriage on said bearing, and control means for all said power means onsaid platform.

6. In the combination of claim 1, the feature that said platform has anoperators stand at one side of the axis of rotation of said platform,and a source of hydraulic pressure on a diametrically opposed side ofsaid platform, said means whereby said carriage is moved verticallycomprising a hydraulic motor on said carriage, and means connecting saidhydraulic motor to said source of hydraulic pressure.

7. In the combination of claim 1, the feature that said carriage has ahydraulic motor and said platform has a source of fluid pressurethereon, and a hose connected at one end thereof to said hydraulicpressure source and at the other end to a conduit fixed, on saidcarriage, said fixed conduit and hydraulic pressure source being sopositioned relatively to said hose that said hose forms a substantialUbetween said fixed conduit and said hydraulic pressure when saidplatform is rotated to a point substantially midway of two extremepoints relatively to said carriage.

8. In a combination of the class described, a mast, a carriage, ahorizontal circular bearing on said carriage, a platform mounted on saidbearing for rotation relatively to said carriage, said carriage andplatform having each an opening within the area outlined by thecircumference of said circular bearing, means mounting said carriage forvertical movement on said mast with said mast extending through bothsaid openings so that said carriage and platform may be elevatedrelatively to said mast, and means for moving said carriage verticallyrelatively to said mast.

9. In the combination of claim 8, an upper base, a mast mounted at itsupper end on said base and extending downwardly from said upper base,and means mounting said first mast for vertical movement relatively tosaid second mast with said second mast also extending through the saidopenings so that said carriage and platform may be elevated relativelyto both masts.

10. In the combination of claim 8, the feature that said platform has anoperators stand at one side of the axis of rotation of said platform anda source of hydraulic pressure on a diametrically opposed side of saidplatform, said means whereby said carriage is moved verticallycomprising a hydraulic motor on said carriage, and means connecting saidhydraulic motor to said source of hydraulic pressure.

11. In the combination of claim 8, the feature that said carriage has ahydraulic motor and said platform has a source of fluid pressurethereon, and a hose connected at one end 12. In the combination of claim8, the feature that said means whereby said carriage is moved verticallycomprises a rack secured to a vertical surface of said mast and a motordriven pinion on said carriage.

13. In the combination of claim 12, the feature that said pinion isdriven through the intermediary of irreversible gears

1. In a combination of the class described, an upper base mounted forhorizontal movement relatively to an upper structure, a verticallypositioned mast fixed at its upper end to said base so as to become anintegral rigid part thereof, a movable mast mounted for verticalmovement on said rigid mast, means for imparting vertical movement tosaid movable mast relatively to said rigid mast, a carriage mounted forvertical movement on said movable mast, means whereby said carriage ismoved vertically relatively to said movable mast and together with saidmovable mast relatively to said rigid mast, said carriage having avertical opening for the passage of both said masts whereby saidcarriage may be lifted vertically relatively to both said masts whilecompletely encompassing both said masts, said carriage having ahorizontal circular bearing formed outwardly about said verticalopening, and a platform rotatably mounted on said circular bearing andalso formed with an opening for said masts.
 2. In the combination ofclaim 1 the feature that said means whereby said carriage is movedvertically comprises a rack secured to a vertical surface of saidmovable mast and a motor driven pinion on said carriage.
 3. In thecombination of claim 2, the feature that the motor driving said pinionis a hydraulic motor, a source of hydraulic pressure for said motor onsaid platform, and means for connecting said source of hydraulicpressure to said motor.
 4. In the combination of claim 4, the featurethat said means for connecting said source of hydraulic pressure to saidmotor is a hose connected at one end thereof to said hydraulic pressuresource and at the other end to a conduit fixed on said carriage, saidfixed conduit and hydraulic pressure source being so positionedrelatively to said hose that said hose forms a substantial U betweensaid fixed conduit and said hydraulic pressure source when said platformis rotated to a point substantially midway of two extreme pointsrelatively to said carriage.
 5. In the combination of claim 1, thefeature that the means for imparting vertical movement to said movablemast are power operated, independent power means comprising the meansfor lifting and lowering said carriage, power means for rotating saidplatform relatively to said carriage on said bearing, and control meansfor all saId power means on said platform.
 6. In the combination ofclaim 1, the feature that said platform has an operator''s stand at oneside of the axis of rotation of said platform, and a source of hydraulicpressure on a diametrically opposed side of said platform, said meanswhereby said carriage is moved vertically comprising a hydraulic motoron said carriage, and means connecting said hydraulic motor to saidsource of hydraulic pressure.
 7. In the combination of claim 1, thefeature that said carriage has a hydraulic motor and said platform has asource of fluid pressure thereon, and a hose connected at one endthereof to said hydraulic pressure source and at the other end to aconduit fixed on said carriage, said fixed conduit and hydraulicpressure source being so positioned relatively to said hose that saidhose forms a substantial U between said fixed conduit and said hydraulicpressure when said platform is rotated to a point substantially midwayof two extreme points relatively to said carriage.
 8. In a combinationof the class described, a mast, a carriage, a horizontal circularbearing on said carriage, a platform mounted on said bearing forrotation relatively to said carriage, said carriage and platform havingeach an opening within the area outlined by the circumference of saidcircular bearing, means mounting said carriage for vertical movement onsaid mast with said mast extending through both said openings so thatsaid carriage and platform may be elevated relatively to said mast, andmeans for moving said carriage vertically relatively to said mast.
 9. Inthe combination of claim 8, an upper base, a mast mounted at its upperend on said base and extending downwardly from said upper base, andmeans mounting said first mast for vertical movement relatively to saidsecond mast with said second mast also extending through the saidopenings so that said carriage and platform may be elevated relativelyto both masts.
 10. In the combination of claim 8, the feature that saidplatform has an operator''s stand at one side of the axis of rotation ofsaid platform and a source of hydraulic pressure on a diametricallyopposed side of said platform, said means whereby said carriage is movedvertically comprising a hydraulic motor on said carriage, and meansconnecting said hydraulic motor to said source of hydraulic pressure.11. In the combination of claim 8, the feature that said carriage has ahydraulic motor and said platform has a source of fluid pressurethereon, and a hose connected at one end thereof to said hydraulicpressure source and at the other end to a conduit fixed on saidcarriage, said fixed conduit and hydraulic pressure source being sopositioned relatively to said hose that said hose forms a substantial Ubetween said fixed conduit and said hydraulic pressure source when saidplatform is rotated to a point substantially midway of two extremepoints relatively to said carriage.
 12. In the combination of claim 8,the feature that said means whereby said carriage is moved verticallycomprises a rack secured to a vertical surface of said mast and a motordriven pinion on said carriage.
 13. In the combination of claim 12, thefeature that said pinion is driven through the intermediary ofirreversible gears.